diff --git a/ext/ereg/ereg.c b/ext/ereg/ereg.c
index 0335347b396..13e06ba3cc6 100644
--- a/ext/ereg/ereg.c
+++ b/ext/ereg/ereg.c
@@ -342,6 +342,7 @@ PHPAPI char *php_reg_replace(const char *pattern, const char *replace, const cha
 			while (*walk)
 				if ('\\' == *walk
 					&& '0' <= walk[1] && '9' >= walk[1]
+					&& walk[1] - '0' <= re.re_nsub
 					&& subs[walk[1] - '0'].rm_so > -1
 					&& subs[walk[1] - '0'].rm_eo > -1) {
 					new_l += subs[walk[1] - '0'].rm_eo
@@ -369,6 +370,7 @@ PHPAPI char *php_reg_replace(const char *pattern, const char *replace, const cha
 			while (*walk)
 				if ('\\' == *walk
 					&& '0' <= walk[1] && '9' >= walk[1]
+					&& walk[1] - '0' <= re.re_nsub
 					&& subs[walk[1] - '0'].rm_so > -1
 					&& subs[walk[1] - '0'].rm_eo > -1
 					/* this next case shouldn't happen. it does. */
diff --git a/ext/standard/reg.c b/ext/standard/reg.c
index 0335347b396..13e06ba3cc6 100644
--- a/ext/standard/reg.c
+++ b/ext/standard/reg.c
@@ -342,6 +342,7 @@ PHPAPI char *php_reg_replace(const char *pattern, const char *replace, const cha
 			while (*walk)
 				if ('\\' == *walk
 					&& '0' <= walk[1] && '9' >= walk[1]
+					&& walk[1] - '0' <= re.re_nsub
 					&& subs[walk[1] - '0'].rm_so > -1
 					&& subs[walk[1] - '0'].rm_eo > -1) {
 					new_l += subs[walk[1] - '0'].rm_eo
@@ -369,6 +370,7 @@ PHPAPI char *php_reg_replace(const char *pattern, const char *replace, const cha
 			while (*walk)
 				if ('\\' == *walk
 					&& '0' <= walk[1] && '9' >= walk[1]
+					&& walk[1] - '0' <= re.re_nsub
 					&& subs[walk[1] - '0'].rm_so > -1
 					&& subs[walk[1] - '0'].rm_eo > -1
 					/* this next case shouldn't happen. it does. */